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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_typetraits.examples.fill"></a><a class="link" href="fill.html" title="An Optimised Version of std::fill">An Optimised Version
      of std::fill</a>
</h3></div></div></div>
<p>
        Demonstrates a version of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">fill</span></code>
        that uses <code class="computeroutput"><a class="link" href="../reference/has_trivial_assign.html" title="has_trivial_assign">has_trivial_assign</a></code>
        to determine whether to use <code class="computeroutput"><span class="identifier">memset</span></code>
        to optimise the fill operation (see <a href="../../../../examples/fill_example.cpp" target="_top">fill_example.cpp</a>):
      </p>
<pre class="programlisting"><span class="comment">//</span>
<span class="comment">// fill</span>
<span class="comment">// same as std::fill, but uses memset where appropriate</span>
<span class="comment">//</span>
<span class="keyword">namespace</span> <span class="identifier">detail</span><span class="special">{</span>

<span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">I</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">b</span><span class="special">&gt;</span>
<span class="keyword">void</span> <span class="identifier">do_fill</span><span class="special">(</span><span class="identifier">I</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">I</span> <span class="identifier">last</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">val</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/integral_constant.html" title="integral_constant">integral_constant</a><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">,</span> <span class="identifier">b</span><span class="special">&gt;&amp;)</span>
<span class="special">{</span>
   <span class="keyword">while</span><span class="special">(</span><span class="identifier">first</span> <span class="special">!=</span> <span class="identifier">last</span><span class="special">)</span>
   <span class="special">{</span>
      <span class="special">*</span><span class="identifier">first</span> <span class="special">=</span> <span class="identifier">val</span><span class="special">;</span>
      <span class="special">++</span><span class="identifier">first</span><span class="special">;</span>
   <span class="special">}</span>
<span class="special">}</span>

<span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">&gt;</span>
<span class="keyword">void</span> <span class="identifier">do_fill</span><span class="special">(</span><span class="identifier">T</span><span class="special">*</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">last</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">val</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/integral_constant.html" title="integral_constant">true_type</a><span class="special">&amp;)</span>
<span class="special">{</span>
   <span class="identifier">std</span><span class="special">::</span><span class="identifier">memset</span><span class="special">(</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">val</span><span class="special">,</span> <span class="identifier">last</span><span class="special">-</span><span class="identifier">first</span><span class="special">);</span>
<span class="special">}</span>

<span class="special">}</span>

<span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">I</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span>
<span class="keyword">inline</span> <span class="keyword">void</span> <span class="identifier">fill</span><span class="special">(</span><span class="identifier">I</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">I</span> <span class="identifier">last</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">val</span><span class="special">)</span>
<span class="special">{</span>
   <span class="comment">//</span>
   <span class="comment">// We can do an optimised fill if T has a trivial assignment </span>
   <span class="comment">// operator and if it's size is one:</span>
   <span class="comment">//</span>
   <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/integral_constant.html" title="integral_constant">integral_constant</a><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">,</span>
      <span class="special">::</span><span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/has_trivial_assign.html" title="has_trivial_assign">has_trivial_assign</a><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">value</span> <span class="special">&amp;&amp;</span> <span class="special">(</span><span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">T</span><span class="special">)</span> <span class="special">==</span> <span class="number">1</span><span class="special">)&gt;</span> <span class="identifier">truth_type</span><span class="special">;</span>
   <span class="identifier">detail</span><span class="special">::</span><span class="identifier">do_fill</span><span class="special">(</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">val</span><span class="special">,</span> <span class="identifier">truth_type</span><span class="special">());</span>
<span class="special">}</span>
</pre>
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<td align="right"><div class="copyright-footer">Copyright © 2000, 2011 Adobe Systems Inc, David Abrahams,
      Frederic Bron, Steve Cleary, Beman Dawes, Glen Fernandes, Aleksey Gurtovoy,
      Howard Hinnant, Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander
      Nasonov, Thorsten Ottosen, Roman Perepelitsa, Robert Ramey, Jeremy Siek, Robert
      Stewart and Steven Watanabe<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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